点击登录前查看是否要保存密码：
private void btn_login_Click(object sender, EventArgs e){if (this.txt_username.Text.Trim() == ""||this.txt_password.Text.Trim() == ""){MessageBox.Show("用户名或者密码为空！");return;}if (this.txt_password.Text.Trim() == "admin"){if (checkbox_savePassword.Checked == true){Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);config.AppSettings.Settings["login_password"].Value = this.txt_password.Text.Trim();config.Save();//System.Configuration.ConfigurationManager.AppSettings.Set("login_password", this.txt_password.Text.Trim());}else {Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);config.AppSettings.Settings["login_password"].Value = "";config.Save();//System.Configuration.ConfigurationManager.AppSettings.Set("login_password", "");}FrmMain frm = new FrmMain();frm.Show();this.Visible = false;}else {MessageBox.Show("登录密码不正确！");}}
配置app.config的文件
<?xml version="1.0" encoding="utf-8"?>
<configuration><appSettings><add key="number" value="0.001" /><add key="login_password" value="" /></appSettings><connectionStrings><add name="DefaultConnection" connectionString="Data Source = |SQL/CE|" /></connectionStrings>
<startup><supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" /></startup><runtime><assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"><dependentAssembly><assemblyIdentity name="System.Runtime.CompilerServices.Unsafe" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" /><bindingRedirect oldVersion="0.0.0.0-4.0.5.0" newVersion="4.0.5.0" /></dependentAssembly><dependentAssembly><assemblyIdentity name="System.Buffers" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" /><bindingRedirect oldVersion="0.0.0.0-4.0.3.0" newVersion="4.0.3.0" /></dependentAssembly></assemblyBinding></runtime>
</configuration>